Check Powershell directory in IIS on the problem server. Make sure SSL is not required.
Allow only Anonymous access – no basic/IWA auth etc.
If you can get into Windows Powershell Modules, run the set-user command suggested above from there.
Remove-powershellvirtualdirectory, and then New-powershellvirtualdirectory (either remotely or using Windows Powershell Modules.
Re-check SSL/authentication once this is done.
Also run iisreset command when completed if you made any changes to any IIS directories.
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